The invention is directed to wheelchairs, and more particularly to front anti-tip wheels for power wheelchairs. However, various aspects of the invention may be used in other applications.
Power wheelchairs are known and have been the subject of increasing development efforts to provide disabled persons with independent mobility. Early power wheelchairs resemble conventional wheelchairs, having a drive wheel at the back of the chair. One difficulty associated with rear wheel drive wheelchairs is that they typically have very wide turning radiuses. The front or mid-wheel power wheelchair is an improvement over these early power wheelchairs. Among other advantages, front or mid-wheel power wheelchairs have tighter turning radiuses. Both front and mid-wheel drive wheelchairs will be hence forth referred to generally as mid-wheel power wheelchairs. Many improvements upon conventional mid-wheel power wheelchairs have been made. U.S. Pat. No. 5,944,131 to Schaffner et al., which is incorporated herein, discloses an improved mid-wheel power wheelchair.
One of the difficulties with mid-wheel power wheelchairs is the tendency to tip in a forward attitude during a sudden stop or while driving down an incline. In response to this problem, anti-tip wheels have been added to the front of power wheelchairs. One mid-wheel power wheelchair embodying front anti-tip wheels is disclosed in U.S. Pat. No. 5,848,658 to Pulver. The anti-tip wheels typically are attached to an arm or suspension system which suspends the anti-tip wheels some distance above the ground. The suspension of the wheels above the ground is necessary so that the wheelchair can clear small obstacles in its path of travel and turn without skidding the wheels sideways. This configuration, however, allows the wheelchair to tip slightly in a forward attitude before the anti-tip wheels engage the ground. Although the anti-tip wheels prevent the wheelchair from tipping over fully, the conventional system allows a partial tip of the wheelchair when a sudden stop occurs or while traveling down an incline. Such a partial tip is a highly uncomfortable and upsetting experience for the user. The present invention solves the problem of partial tipping of the wheelchair.